Speed controller for prime movers



Apri] 15, Wi FERRIS SPEED CONTROLLER FOR PRIME MOVERS Filed Sept. 28, 1956 4 Sheets-Sheet l Inn/ENTER VVLTER FERRIS BY WTTDRNEY.

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m CL T3) u April l5, 194l w. FERRls SPEED CONTROLLER FOR PRIME MOVERS 4 Sheets-Sheet 3 Filed sept. 28. 193s S m e Q Q E D w o mm.. m v N R v T .l E Q Q U am. .www WH Vl B m w m. 8 T 6` T S mw Nm n u mm Y m e A vm w um.

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4 Sheets-Sheet 4 Filed Sept`. 28, 1936 NVU I om bw INVENTDR NYALTER FERRIS E ATTUHNEY.

Patented Apr. 15, 1941 52,238,218 sPEEp'CoNTiiLLEa Fon PRIME MovERs Walter Ferris, Milwaukee, Wis.

apbucanon september 28,1936, serial No. 102,850

17 Claims.

This application is a continuation in part of my copending application Serial No. 47,008, filed October 2B, 1935 which has since matured into Patent No. 2,198,035.

The invention relates to speed controllers for prime movers and it is particularly adapted for controlling prime movers the speels of which vary in response to variations in the loads thereon.

The speeds of certain prime movers such as synchronous electric motors, remain substantially constant under varying loads but the speeds of other prime movers, such as direct current and induction motors, steam engines and gasoline enzines, decrease as the loads thereon increase and increase as the loads thereon decrease. Even the speed of a synchronous motor is not absolutely constant for the reason that the frequency of the power circuit iluctuates more or less even when the generator supplying power to the circuit is controlled by chronometric medianisms which presumably keeps the frequency constant but which in'practice simply keeps, the overall frequency constant during a given period of time, for instance 8 to 12 minutes, so that electric clocks may be operated from the circuit.

In certain processes, it is very desirable that a machine or a machine part be operated at a constant adjustable speed` or at a uniformly varying speed but the variable speed prime movers now in use will not operate at uniform speeds under varying loads.

If it is attempted to maintain the speed of a... variable speed prime mover constant or at a uniformly varying rate by means of a controller which is operated at least in part by a synchronous motor, such as the disk type controller shown in my copending application referred to above. the variations in the speed of the synchronous motor will prevent the controller from maintaining prime mover speed constant or`at l'a uniformly varying rate. The controller shown in that application will keep the prime mover speed within closer limits than was previously possible, nevertheless the errors in the speed of less of variations inthek supply of energy to the as reflected in the tendency to vary the speed of the prime mover.

According to the invention inanother aspect, the prime mover drives in addition to its useful load a small capacity pump which delivers its output through a resistance and thereby exerts a brake load upon the prime mover. The resistance is adjusted in response to any movement of the output leg of a three legged diierential which has one of its input legs driven by the prime mover and its other input leg driven at a constant' speed under the control of the chronometric mechanism, whereby any variation in the prime mover speed changes the ratio between the speed of the two input legs of the diiferential and thereby causes the output leg thereof to move 4and adjust the resistance with a resultant variation in the brake load on the prime mover.

According to the invention in another aspect, means are provided for varying the brake load on the prime mover to correct limited variations in prime mover speed, and additional means are a synchronous motor will be reflected by variation in the speed of the prime mover.

`The present invention has as an object to provide a controller which will maintain the speed of a prime mover substantially constantsunder varying loads.

Another object is to provide a controller of the above character which will maintain the speed of a prime mover substantially constant regardprovided for varying the flow of energy to the prime mover to anticipate and prevent wider variations in prime mover speed.

The invention is exemplified by the controllers shown schematically in the accompanying drawings in which thewiews are as follows:

Fig. 1 is aschematic view showing the controller as being employed to control the speed of a small capacity prime mover by applying a brake load to the prime mover and varying it in response to variations in primemover speed.

Fig. 2 isa central longitudinal section through a throttle valve which is ordinarily employed in the controller shown in Fig. I.

Fig. 3 is a `transverse section taken on the line 3 3 of Fig. 2.

Fig. 4 is an outside view of a part of a sleeve control the speed.

which channel 1 communicates. Groove :municates with the and shows the shape of the oriiice formed therein.

Fig. is a view similar to Fig. 1 but showing employed to control the speed o!" Fig. 6 is a view similar tolFig. 5 but showing the controller provided with means for varying the flow of energy to the motor in definite steps.

While for the purpose of illustration the invention has been shown embodied in controllers for electric motors, it is adaptable to the control of other types of prime movers the-speeds of which vary in response to variations in the loads thereon and, while comprises a pump be controlled and dissipating by throttle valve a part of the energy the prime mover, a friction or other may be used to dissipate thefenergy driven by the prime mover to delivered by type brake and thus Fig. 1

' The controller is shown in this figure as being employed to control the speed o! an lelectric motor I which is shown connected to an electric generator 2 to drive the same. Generator 2 may be of the synchronous type and employed to generate current for energizing synchronous motors which drive speed control devices, such as the disk type control unit of the transmission shown inthe application referred to above.

Motor I is provided with a brake shaft 3 which is connected through a drive l to a gear pump 5 to drive the same. Gear pump 5, which functions to exert a brake load upon the motor l, draws liquid from a reservoir 6 formed in the base of the pump casing and discharges it into a channel 1.

The discharge of liquid through channel 1 by pump 5 is resisted by a throttle is operated in response to variations in the speed of motor I and varies the resistance to the flow of liquid through channel 1 to thereby vary the brake load on motor I.

For simplicity in illustration, valve 3 has been shown in Fig. 1 as being provided with a valve member or plunger 9 which Ais closely fitted in the bore of a sleeve l0 to reciprocate therein. Sleeve I0 is tightly fitted in a vlave body II having formed therein around `sleeve I0 a groove' I2 with I2 comtwo or more orifices f I3 which are formed in the wall of sleeve I0 and are somewhat triangular in shape. Only one or-ice I3 has Fig. 1 but two or more are ordinarily provided and equally spaced around sleeve I0 in order that valve member 9 may be hydrostatically balanced. Liquid at a rate determined by the position of valve member 9, from groove I2 through orifices I3 into the bore of sleeve I0 from which it may escape into a suitable exhaust channel connected thereto. J

In practice, a valve member 9 of the type shown in Figs. 2, 3 and 4 is ordinarily employed. This valve member consists primarily of a part Se, which is closely fitted inthe bore of sleeve I0 to reciprocate therein, a part 9b which is considerably smaller in diameter than part 9 and formed integral therewith, and a sleeve [3 which is pressed onto part a short distance from lthe end a narrow annular groove 9d therebetween.

9b with its left end spaced of part 3'* to form The the brake mechanism shown means of a valve 8 which bore of sleeve I0 throughv suitable source. As shown,

sectional area of groove 8d.

Groove Sid has its narrow outer part in communication at all times with the orices I3 in sleeve Iii and its wider inner part in communication at all times through a plurality of radial ducts 9e with an axial bore 8f which extends throughout 'the length of part SlSL and into part 9b. In order to prevent groove 9d from passing out of registry with orifices I3 when valve member S is shifted toward the-left, sleeve 9C has a flange 9 formed upon its outer end .and so positioned that it ywill abut the end of sleeve I0 when groove 9d registers with the left ends of orifices I3.

The arrangement is such that liquid may flow from channel 1 through groove I2, orifices I3, groove 9d, ducts 3e, bore Si and the bore in sleeve I0 into the exhaust channel. When iiange 3 is in contact with the end of sleeve II), groove 9d will register with the widest part of each orice I3 and the resistance to the discharge of liquid from pump 5 will be the least.

Moving valve member decrease the effective areas of orifices I3. That is, as valve member 9 is moved toward the right, groove 9d will register with narrower parts of oriiices I3, and consequently increase the resistance to the flow of liquid therethrough, until groove 9d registers with the right ends of orifices I3 at which time the effective .areas of orlflces I3 will be the smallest and the yresistance to the discharge of liquid from pump 5 will be the greatest.

Valve member 9 is urged by a spring I4 toward the left or in a direction to increase the effective areas of orifices I3, and it is adapted to be moved toward the right or in a direction to decrease the effective areas of orices I3 by a mechanism which will be presently described and which engages a lug I5 iixed to the stem of valve member 9.

The movement of valve member 9 toward the left is preferably retarded as by means of a dashlpot. As shown, II has a bore I6 and a counterbore I1 formed therein concentric with the bore in sleeve I0 and communicating therewith. A dashpot plunger I8 has its head closely fitted in counterbore in bore I6 and extending therethrough into contact with the left end of valve member 9.

The right or front end of counterbore I1 has a drain channel I9 connected Ithereto to permit liquid to escape freely therefrom, of counterbore I1 are connected to each other by a channel 20 to permit plunger I8 to eject liquid from the left or rear end of counterbore I1.. Channel 2li-has a limit the rate of flow limit the rate of movement of valve member 9 when retracted by spring I4.

Liquid may be supplied to the left end of counterbore I1 from any suitable source which will supply it thereto at a low lpressure which is suflicient to enable the liquid to move plunger I8 and hold it -in contact with the left end of valve member 9 but which is not great enough to affect the accurate operation of valve 8. As shown, liquid is supplied to counterbore I1'y from a supply tank 22 through a channel 23 and a check valve 24 which permits liquid to flow from tank 22 into counterbore l1 but prevents it from flowing in the opposite direction.

Tank 22 maybe supplied with liquid from any an exhaust channel 25 has its upper end arranged to discharge into 9 toward the right wiu I1 and its vstem closely fittedv and both ends restricted oriiice 2l therein to y therethrough and thereby tank 22 and its lower end connected to valve body II in communication with the interior oi' sleeve III at a point beyond valve member 9 so that all liquid passing through valve'8 is discharged into tank 22.

The volume of liquid passing through valve 8 is greater than the volume required to keep tank 22 filled. For the purpose of illustration, tank 22 is shown connected near its upper end to reservoir 6 by an overflow channel 28 to which channel I9 is also connected. Channel 28 permits the overflow from tank 22 and all liquid discharged from the right end of counterbore Ilv to be returned freely to reservoir 6. In practice, however, the entire controller is arranged within an oil tight casing, ltank 22 and overflow channel 28 are omitted, and the upper end of channel 23 is arranged high enough-to provide the proper head and the liquid for operating the dashpot is discharged into the open end thereof as the overow does no harm.

When valve member 9 moves toward the right, liquid will flow through check valve 24 into the left end of counterbore l1 and move plunger I8 toward the right so that its stem remains substantially in contact with the end of valve member 9. vVhen valve member 9 stops moving toward the right, check valve 24 will close so that, when valve member 9 is moved toward the left by spring I4 and moves plunger I8 with it, plunger I8 will have to eject liquid from the left end of counterbore I 'I through channel 20 and orifice 2I, thereby retarding the action of spring I4 and causing valve member 9 to move toward the left at a rate determined by the resistance of orifice 2| The mechanism for operating valve 8 is substantially the same as the'corresponding mechanism illustrated and described in my copending application referred to above, consequently, it is not illustrated nor described in detail herein. It is deemed sufficient to state that this mechanism includes a three legged differential 30 which has one of its legs driven at a speed proportional to the speed of motor I, a second leg driven at a measured speed and a third leg arranged to operate valve 8 so that any variation in the ratio between the speeds of the rst two legs will result in movement of the third leg with resultant operation of valve 8.

As shown, differential 30 includes an internal gear 3l which is driven from shaft 3 by a drive 32 and forms one leg of the differential, a sun gear 33 which is fixed on a shaft 34 and forms the second leg of the differential, and a planet pinion 35 which meshes with both of gears 3| and 33 and forms a part ofthe third leg of the differential.

' Planet pinion 35 is arranged upon a shaft 36 which is carried by a crank 3l at the outer end thereof.l Crank 31 is fixed upon one end of a shaft 38 having an operating lever 39 arranged thereon and fixed for rotation therewith by a snap clutch connection. As shown, lever 39 has its hub journaled upon shaft 38 and provided in one of its ends with notches 40, a pin 4| is fixed in shaft 38, and a spring 42 urges lever 39 along shaft 38 to hold one of notches 40 over pin 4I.

The lower end of lever 39 is arranged between the lug I5 on the stem of valve 8 and a stationary stop 43 so that, when lever 39 is swung toward the right, it will operate valve 8 and, if

it should be swung too far toward the left, it Y,

would engage stop 43 before passing beyond its effective range. Further rotation of shaft 38 direction, thus providing a constant clockwise driving torque proportional to the mass and radius of the weight. 'I'his torque is continuously applied to crank 3l and `by it transmitted through shaft 36,-planet pinion 35 and sun gear 33 toshaft 34 which is thus driven in a clockwise direction by a constant force.

The speed of shaft 34 is controlled by a chronometric mechanism 50 which includes an escape wheel 5I'fixed upon shaft 34. 'I'he teeth of escape wheel 5I are engaged by two pallets 52 extending from opposite sides of an escape lever 53 which is pivoted above escape wheel 5I upon a stationary pivot 54.

A stiff rod 55 has its upper end fixed to escape lever 53 and its lower end fitted in and freely slidable through a pendulum bob 56 which is supported by two thin and flexible ribbons 51 and 58 from two drums 59 and 60. Ribbon 51 passes over drum 59 and both ribbons are fastened to drum so that rotation of drum 60 will lengthen or shorten the pendulum.

Rotation of brake shaft 3 rotates differential gear 3| in a counterclockwise direction at a speed proportional to the speed of motor I. Gear 3|, acting through pinion 35 and sun gear 33, tends to rotate shafts 34 and 38 in opposite directions but, since rotation of shaft 38 by gear 3| is resisted by weight 45, gear 3I tends to rotate shaft 38 in a clockwise direction at a speed proportional to the speed of prime mover I but it cannot do so for the reason that pallets 52` engage the teeth of escape wheel 5I intermittently and prevent rotation of shaft 34 during the larger part of each pendulum swing, thereby causing gear 3I through pinion 35 to rotate shaft 38 in a counterclockwise direction and raise weight 45. As each pallet 52 releases a tooth of escape wheel 5I, Weight 45 drops suddenly and transmits a driving force through differential 50, thereby rotating shaft 34 at high speed in a clockwise direction until the other pallet 52 engages a tooth of escape wheel 5|.

Shaft 34 is thus intermittently rotated at a constant overall speed which is proportional to the frequency of the pendulum, and shaft 38 during each cycle of the pendulum is oscillated and swings lever 39 gradually toward the right and then suddenly toward the left through a limited arc.

As long as the speed of gear 3I remains proportional to the overall speed of shaft 34, the net rotation of shaft 38 will be zero and lever 39 and Weight 45 will be swung through arcs the lengths of which remain substantially constant.

If the speed of gear 3| should increase or if the speed of sun gear 33 should decrease, planet pinion 35 would be carried around in a counterclockwise direction, simultaneously lifting weight 45. 'I'his movement of planet pinion 35 results from the teeth being driven on one side by gear 3I and held back on the other side by sun gear 33. Conversely, if the speed of gear 3| should decrease or if the speed of gear 33 should increase, planet pinion 35 would be carried around in a clockwise direction thereby rotating shaft 38 in the same direction and lowering weight 45.

As previously explained, shaft 38 swings lever 39 through a limited arc first in one direction and then in the opposite direction during each cycle of the pendulum. If lever 39 were 'connected to valve 8, it would shift the valve B a substantial distance in each direction and thereby cause a considerable uctuation in the brake load on motor l although the net brake load over a plurality of oscillations would remain constant as long as the `motor speed remained constant.

With the construction shown however, lever 39 simply contacts lug i5 and then moves valve 8 toward the right a very short distance. near the end of each lifting movement of weight 45l Then when weight 45 falls, lever 39 swings suddenly toward the left out of contact with lug l5 and permits spring i4 to shift valve 8 toward the left. However, spring i4 is opposed by dashpot l'l-i and is able to move valve 8 through only a very short distance before lever 39 again swings toward the right and returns valve 8 to its previous position with the result that the net brake load on motor I remains constant and the momentary iiuctuation in brake load is very small.

If the speed of motor i should increase due to any cause, such as a reduction in useful load thereon or a variation in frequency in the energizing current, gear 3i would be accelerated relative to the speed of sun gear 33 and cause planet pinion' 35 to rotate shaft 3B in a counterclockwise direction and thereby shift the operating arc of lever 39 in a counterclockwise direction so that valve B would be shifted toward the right to reduce the effective areas of orifices i3 and thereby increase the brake load until motor i was decelerated to the desired speed.

If the speed of motor i should decrease due, for instance, to a variation in the frequency or useful load, gear 3l would be decelerated relative to the speed of sun gear 33 and cause planet pinion 35 to rotate shaft. 38 in a clockwise direction and thereby shift the operating arc of lever-39 in a clockwise direction so that valve 6 will be shifted toward the left to increase the effective areas of orifices i3 and thereby decrease the brake load until motor l was accelerated to the desired speed.

After each correction of motor speed, lever 39 will oscillate in its new range and the controller will continue to function in the above described manner until another variation in useful load or frequency causes another variation in motor speed at which time lever 39 will be shifted to another range to correct such variation.

The controller shown in Fig. l. thus maintains the speed of a prime mover constant by applying a brake load thereon and varying the brake load in response to variations in prime mover speed. It is intended to be employed for controlling only prime movers of small capacity or prime movers the loads on which vary through a very limited range as otherwise the power wasted in overcoming the brake load would render the controller uneconomical.

in order to avoid undue waste of power when the controller is employed to maintain constant the speed of a larger capacity prime mover which drives a variable load, the controller may be provided with means for varying the flow of energy to the prime mover in addition to the means for applying a brake load thereon and varying the brake load in response to variations in prime mover speed. The brake load may be varied to compensate for slight variations in the useful load or, in the case of an electric motor, to compensate for slight variations in the frequency or voltage of the energizing current, and the flow of energy to the prime mover may be varied to compensate for wider variations in load or energizing current.

For the purpose of illustration, the controller is shown in each of Figs. 5 and 6 as being employed to control the speed of an electric motor by varying a brake load thereon to compensate for slight variations in useful motor load or slight variations in the frequency or voltage of the energizing current and by varying the field strength of the motor to compensate for Wider variations in load or frequency but it is to be understood that the controller may as readily be employed to control the speed of other types of prime movers by simply replacing the rheostat which controls the field strength with a controllersuitable to the particular type of prime mover to be controlled.

Fig. 5

The controller is shown in this figure as being A employed to control the speed of an electric motor I which drives a useful load such as a generator 221. Variations in the speed of motor I"L due to wide variations in either the useful load or in the voltage of the energizing current are corrected by varying the strength of the motor eld while variations in motor speed due to limited variations in load voltage or frequency are corrected by applying a greater or a lesser brake load upon the motor.

As shown, the field strength may be varied by a rheostat 65 which is connected in circuit with the field winding of the motor. All of the details and electric connections of rheostat 65 have not been shown as such rheostats are well known and as it is common practice to employ rheostats for the purpose indicated. It is deemed suflcient to state that rheostat 65 includes a socalled stepless resistor 66 and a contact arm 61 which has one of its ends in contact with resistor 66 and its other end pivoted upon a stationary bracket 68.

The means for applying a brake load to motor IL1 is identical in part to the corresponding mechanism shown in Fig. 1 and previously described. Consequently, identical parts have been indicated by identical reference numerals and no further description thereof will be given While other parts which are similar but not identical to the corresponding parts shown in Fig. 1 have been indicated by corresponding reference numerals with the exponent a added.

Briefly, the brake shaft 3' previously described is fixed to the rotor of motor Ia and driven thereby. Shaft 3 drives gear pump 5 through drive 4 and it drives gear 3| of differential 30 through drive 32 at a speed proportional tothe speed of the motor la. Shaft 34 of differential 30 is rotated at a measured speed under the control of chronometric mechanism 50 so that any variation in the speed of motor I will cause shaft 38 of differential 30 to rotate in one direction or the other depending upon whether the motor speed increases or decreases'in respect to the speed of shaft 34 as previously explained.

Gear pump 5 has its outlet connected by channel 1 to the inlet of a throttle. valve 8 which is adjusted to provide an initial resistance to the flow of liquid therethrough and thereby enable gear pump 5 to exert a brake load upon motor l,

.Valve 8a is exactly the same as the valve 8 previously described except that the dashpot I'l--l assuma E5 is omitted therefrom and the valve member l has' Motion is transmitted to valve member 84 from its stem connected to the lower end o1' a bar 88 shaft 38 by means of a lever 38which is arranged which is pivoted at its upper end upon a pin 18 I upon shaft 88. Lever 38* is provided with a drivfixed in contact arm 61 near the upper end thereing arm 44 and is the same as the lever 39 preof. Bar 68 is adapted to be swung upon pin 18 5 viously described except that its depending arm to shift valve member s in one direction or the Is somewhat shorter. The depending arm of lever other and thereby vary the brake load on motor 88* is pivoted at its lower end to the upper end of Il, and the distance through which bar 68 may a lever 88 which is adapted to engage a lug I5EL be swung is limited by two stops 1| which are fastened to the stem of valve member 84. Lever fixed in contact arm 61 upon opposite sides of l0 86 has its lower end pivoted by a pin 81 to one bar 68 near the lower end thereof. i end of a follow-up rod 88 the other end of which The mechanism for swinging bar 86 upon 'pin is connected to bar 88 between pin 10 and the 18 includes a hydraulic servo-motor which has point at which servo-motor piston rod 15 is cona cylinder 12 arranged in a stationary position, a nected to bar 88. piston 13 fitted in cylinder 12 and urged toward l5 The arrangement is such that, when a pallet 52 the right by a spring 14, and a piston rod 18 havengages a tooth of escape wheel 5| and causes ing one of its ends fixed to piston 13 and its other shaft 38 to be rotated in a counterclockwise diend pivoted to bar 68 intermediate the ends thererection as previously explained, lever 39e will of. swing lever 88 upon pin 81 and lever 86 will en- Servo-motor 12-13 is adapted to be operated 20 gage lug I 8 and shift valve member 84 toward the by liquid supplied thereto from gear pump 8 right to permit liquid to flow to cylinder 12 and under the control of a valve 16 which functions move piston 13 toward the left with the resultant to open the right end of cylinder 12 either to gear operation of throttle valve 8B and, when the Dumb pressure or to a drain channel 11 which pallet disengages the tooth of the escape wheeldischarges into reservoir 6 and to which the 25 and permits weight 45 to fall and rotate shaft left end of cylinder 12 is connected in order to 38 in a clockwise direction as previously exprevent air or liquid from beiner entr'appedthereplained, lever 39e will quickly swing lever 86 out in. of contact with lug I5a and permit spring I4 to To this end. the right end of cylinder 12 is move valve member 84 toward the left to open connected by a channel 18 to an exit port 'I8 30 cylinder 12 to drain channel 11 and thereby perwhich is formed in the body 80 of control valve mit spring 14 to move piston 13 toward the right 18 between an inlet port 8| and an exhaust port with the resultant operation of throttle valve 8a. 82 also formed therein. Port 8| is connected by The movement of valve mernbe;- 84 toward the a channel 83 to channel 1a intermediate the ends left under the influence of spring I4 is retarded thereof and port 82 has a branch of drain chan- 35 by dashpot I1-I8 so that, so long as the speed nel 11 connected thereto of motor I remains constant, valve member 84 The oW of liquid through port 79 is Controlled moves but little toward the left before link 88 by a valve member 84 which is closely fitted in again engages lug I5El and moves it rtoward the the bore of valve body 80 to reciprocate therein. right. Consequently, piston 13 moves throttle When valve member 84 is in its central or neutral 40 valve member 9 through so narrow/a range that position as Shown, port 19 is blocked so that DiS- the brake load on motor |a varies but little durton '13 is retained in a stationary position by the lng each swing of pendulum 56 and the overall liquid trapped in the right end of cylinder 12. brake load remains constant as long as the motor When valve member 84 is shifted toward the speed remains constant. left from its central or neutral position, port 18 45 When the speed of motor |FL increases above is opened to port 82 so that spring 74 may move normal, shaft 38 will be rotated through a greater piston 13 toward the right and cause it to eject angular distance in a counterclockwise direction liquid from the right end of cylinder 12 through as long as the motor speed continues to increase channel 18 and valve 16 into drain channel 11. and then it will oscillate through the original When valve member 84 is shifted toward the 50 angular distance but in a range or arc which is right from its central or neutral position, port 18 displaced in a counterclockwise direction from is opened to port 8| and liquid may flow from the arc through which it operated when the mochannel 1a through channel 83, valve 16 and tor was running at its normal speed.

channel 18 to the right end of cylinder 12 and Shaft 38 will cause lever 38a to swing the upper move piston 13 toward the left against the re- 55 end of lever 88 farther toward the right and sistance of spring 14. cause lever 88 to shift valve member 84 farther Control valve 16 is operated in exactly the toward the right so that liquid may enter cylinsame manner that throttle valve 8 is operated in der 12 and move piston 13 toward the left. Pisthe controller shown in Fig. l. That is, valve ton 13 will swing bar 68 upon pin 10 and thus member 84 is continually urged toward the left 60 shift throttle valve member 8 toward the left to by a spring i4 and it is moved toward the right reduce the effective areas of orifices I3 and thereeach time the (shaft 38 of differential 30 is roby increase the brake load on motor la. tated in a counterclockwise direction. Swinging bar 69 toward the left causes follow- The movement of valve member 84 toward the up rod 88 to move the pin 81 upon which lever left is retarded by a dashpot |1-I8 which is 65 88 is pivoted toward the left and thereby tend to identical with the dashpot |1|8 previously depermit valve member 84 to move toward the left. scribed and which functions and is supplied with The arrangement is such that valve member 84 is liquid from a tank 22 in the manner previously returned to its normal range of reciprocation the described. All liquid passing through throttle instant that motor I is decelerated to its norvalve 8'al is discharged into tank 22 through a 0 mal speed. channel 25a and all excess liquid is drained from Ii' the brake load does not become great enough tank 22 through an overflow channel 85 which to decelerate motor I* to its normal speed before has one of its ends connected to tank 22 near the throttle valve member 8 reaches the limit of' its upper end thereof and its other connected to effective range, the lower end of bar 89 will endrain channel 11 intermediate the ends thereof. v gage a stop 1| vand then servo-motor 12--13 will 6 move the upper end oi contact arm along re sister 66 to vary the field strength and thereby decelerate motor is.

Followmup rod d8 will move the lower end of lever 8GB toward the left as contact arm Ml moves along resistor il@ so that valve member @il will be returned to its normal range and further movement oi contact arm Si will cease the instant that motor i is decelerated to its normal speed.

Varying the held strength will cause deceleration. of motor i, as previously explained, but motor iZ will not decelerate quite as fast as the held strength is varied so that the field strength is changed a trifle too much before motor is reaches its normal speed. Consequently, deceleration o motor ifi will continue until the motor speed is a trifle below normal with the result that the operating arc or range o lever 3Q is shifted slightly 'in a clockwise direction and spring id is permitted to shift control valve member @di slightly toward the left.

Shifting control valve member fl toward the left will open port 'i9 to port il?. and permit servomotor liv-73 to shift throttle valve member il toward the right to increase the effective areas of orLdces is and thereby decrease the brake load and permit motor i to accelerate to its normal speed at which time lever 3GB will be oscillating in its normal range and the brake load will become constant. The speed of motor ia will then remain constant until again varied due to some cause such as a variation in load or frequency.

.ii the speed of motor l would drop below normal, the brake load will be decreased to permit the motor to accelerate as explained above.. if the motor has not accelerated toits normal speed before the entire brake load is released, the lpwer end of bar 69 will engage a stop 'il and then servo-motor 'i2- 13 will move the upper end of contact arm Si along resistor Sii to vary the field strength and thereby cause further acceleration of the motor.

'Varying the iield strength will accelerate the motor slightly above its normal speed and the brake load will be increased to decelerate the motor to its normal speed as explained above. A braise load is thus available at all times for correcting slight variations in motor speed while larger variations are corrected by varying the ileld strength.

Fig. d

The controller shown in this i'lgure is substann tially the same as the controller shown in i with the exception or" the means for varying the field strength and for operating the throttle vmve. Consequently, those parts oi the two con*1 trollers that are identical have been indicated by identical reference characters and will not be further described.

rThe mechanism for varying the field strength includes a rheostat @il the details and electrical connections ci which have not been illustrated as such rheostats and the application thereof to the control of motors are well known.

Pcheostat E@ includes a stationary resistance member Si and a contact arm Q2 which is pivoted at its lower end upon a stationary shaft S3 and has its upper end in Contact with one o a plurality or" contacts S4 arranged upon resistance mermber Si. Contact arm 92 is yieldingly restrained from rotating upon shaft S3 by a spring pressed plunger 85 which is carried by arm S2 and carries an anti-friction roller Sii which engages one of a plurality of notches ill ormed in a stationfill aesaeis ary arcuate bar 93. Notches 91 are so shaped that the force required to start roller 96 out of its seat in one of notches 91 is greater than the force required to keep it moving toward the next adjacent notch.

Contact arm 92 is provided at its lower end with an internal gear segment 99 which is concentric with shaft 93 and meshes with a gear |00 arranged upon a shaft lill carried by a lever |02 at the upper end thereof. Lever |02 is pivoted intermediate its ends upon shaft 93 and has its lower end connected to the piston rod 'i5 of servo-motor l2-'|3. Follow-up rod 88 is connected to lever 902 at a point between shaft 93 and piston rod l5.

Gear i0@ meshes with a segmental gear |03 formed upon the hub of a lever |04 which is journaled upon shaft 93. Lever |04 is connected at its outer end by a link |05 to one end of a rod i536 the other end of which is connected to the valve member 9 of throttle valve 8B. Rod |06 has an abutment lei fixed thereon intermediate the ends thereof and arranged in a stationary casing i138 between two springs |09 and ||0 which bear against it and against the ends of casing mit.

When springs ill and lill are equally loaded,

there will be no net torce tending to move rod.

ist in either direction and valve member S will be held in its normal position with groove 0d (Fig. 2) approximately midway between the ends of orifices |3 so that approximately one-half the brake load will be applied to motor I".

1f motor i accelerates beyond its normal speed, due either to a variation in the useful load or to a variation in frequency or voltage, gear 3l of differential 30 will be rotated faster rela.- tive to the speed of shaft 34 and cause lever 39* to swing farther in a counterclockwise direction. Lever 39x1 will shift control valve member 04 farther toward the right (Fig. 6) so that liquid from gear pump 5 may enter cylinder 12 and move piston i3 toward the left.

Piston 'i3 will swing the lower end of lever |02 toward the left and cause its upper end to move gear 00 toward the right. Plunger 95 will at rst hold contact arm 92 stationary and, since gear segment 98 is iixed to arm 92, it will remain stationary and cause gear |00 in moving toward the right to rotate in a counterclockwse direction and rotate segmental gear |03 in a clockwise direction. Rotation of segmental gear H03 will cause lever |04, acting through link |05 and rod U05, to move throttle valve member 0 upward and reduce the eiective areas of orifices i3, thereby increasing the brake load and tending to decelerate the motor.

As valve member 9 moves upward to increase the brake load on the motor, abutment |01 will compress spring il@ and, if the motor has not been decelerated to its normal speed by the time the entire brake load has been applied, the force exerted by spring ||0 through rod |06, links |05, lever E04, segmental gear |03, gear |00 and gear segment 9B will be sufficient to overcome the resistance of the spring on plunger 95 and cause contact' arm 92 to move suddenly from one lcontact 94 to the next contact 84 and roller 96 to snap over into the next notch 91,.

Contact arm 92 in moving from one contact 94 to another varies the iield strength to deceierate the motor and simultaneously permits spring lili to expand and shift valve member 0 back to its normal position so that the brake load on the motor is reduced to approximately one-half of full brake load at the same instant that the field strength is varied.

Servo-motor I2-'i3 will continue to swing le-l ver |02 'upon shaft 93 until the motor has been decelerated to its normal speed so that, if the motor speed is not reduced to normal by shifting contact arm 92 from one contact 94 to the next contact 94, continued movement of servo-motor piston 'i3 will cause the brake load to be increased and the field strength varied alternatively in the above described manner until the motor has been decelerated to its normal speed.

If a variation in the useful load or a variation in frequency or voltage causes motor |a to be decelerated below its normal speed, the controller will operate in the reverse of the above described manner to correct such decrease in speed. Briey, a reduction in motor speed below normal will cause gear 3| of differential 30 to be rotated slower relative to the speed of shaft 34 and cause lever 39a to swing farther in a clockwise direction. Lever 39a will permit spring Il to shift control valve member B4 farther toward the left so that liquid may escape from cylinder l2 and permit spring 'H to move piston 13 toward the right.

Piston 'I3 will` swing the lower end of lever |02 toward the right and cause its upper end to move gear toward the left along gear segment 99, thereby causing gear |00 to rotate in a clockwise direction and rotate segmental gear |03 in a counterclockwise direction. Rotation of segmental gear |03 will cause abutment |01 to compress spring |09 and rod |06 to move throttle valve member 9 downward and increase the effective areas of orifices I3, thereby decreasing the brake load and tending to permit the motor to accelerate.

Servo-motor 'l2-13 will continue to swing lever |02 upon shaft 93 until the motor has accelerated to its normal speed so that if the motor has not reached its normal speed by the time the entire brake load has been released, the force stored in spring |09 will be sufficient to cause contact arm 92 to move from one contact 94 to the next contact 94 and valve member 9 to be returned to its normal position as above explained.

After each adjustment of contact arm 92 in one direction or the other, valve member 9 is returned to its normal position so that the brake load may be varied to compensate for small changes in useful load or small changes in frequency or voltage until a large change occurs and then the force stored in spring |09 or 0 becomes sufficient to shift contact arm 92 in one direction or the other to vary the field strength as above explained.

The invention herein set forth is susceptible of various modifications and adaptations Without departing from the scope thereof as yhereafter claimed.

The invention is hereby claimed as follows:

1. A speed controller for a prime mover, comprising means for imposing a brake load upon said prime mover, a three legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg driven at a measured speed whereby any variation ln the speed of said prime mover relative to said measured speed causes rotation of the third leg of said differential, means for varying the flow of energy to said prime mover to thereby vary the speed thereof, and means responsive to rotation of said third leg for first varying the brake load on said prime mover and then operating said energy varying means to thereby correct said variation in prime mover speed.

2. A speed controller for a prime mover, comprising means for imposing a brake load upon said prime mover, a chronometric mechanism, a three legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said chronometric mechanism and driven at a speed proportional to the speed thereof whereby any variation in the speed of said prime mover relative to the speed of said chronometric mechanism causes rotation of the third leg of said differential, means for varying the flow of energy to said prime mover to thereby vary the speed thereof, and means responsive to rotation of said third leg for first varying the brake load on said prime mover and then operating said energy varying means to thereby correct said variation in prime mover speed. Y

3. A speed controller for a prime mover, comprising a three legged differential having a first leg driven by said prime mover at a speed proportjonal to the speed thereof and a second leg driven at a measured speed whereby any variation in the speed of said prime mover relative to said measured speed causes rotation of the third leg of said differential, means for imposing a brake load upon said prime mover to vary the speed thereof, means for varying the flow of energy to said prime mover to vary the speed thereof, a valve for controlling the operation of said brake load imposing means and for controlling the operation of said energy varying means, and means responsive to rotation of the third leg of said differential for operating said valve.

4. A speed controller for a prime mover, comprising a three legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg driven at a measured speed whereby the third leg is rotated in response to any variation in the speed of said prime mover relative to said meas- Y ured speed, a pump driven by said prime mover,

a valve for resisting the discharge of liquid by said pump to thereby impose a brake load upon said prime mover. means for varying the dow of energy to said prime mover to thereby vary the speed thereof, and means responsive to Irotation of the third leg of said differential for first operating said valve to vary the resistance to the now of liquid therethrough and thereby vary the brake load on said prime mover and then operating said energy varying means.

5. A speed controller for a prime mover, comprising a pump driven by said prime mover, a chronometric mechanism, a three legged differ- -ential having a first leg driven by said prime mover at a speed proportional tothe speed thereof and a second leg connected to said chronometric mechanism and driven at a speed proportional to the speed thereof whereby any variation in the speed `of said prime mover relative to the speed of said chronometric mechanismv causes rotation of the third leg of said differential, a valve for resisting the discharge of liquid by said pump to thereby impose a brake load upon said prime mover, means for varying the flow of energy to said prime mover to thereby vary thel speed thereof, and means responsive to rotation of the third leg of said differential for first operating said valve to vary the resistance to the flow of liquid therethrough and thereby vary the brake load upon said prime mover and then operating said energy varying means.

6. .A speed controller for a prime mover, comprising means for imposing a brake load upon said prime mover, a three legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg driven at a measured speed whereby any variation in the speed of said prime mover relative to said measured speed causes rotation of the third leg of. said differential, means for varying the brake load on said prime mover to there by correct slight variations ln prime mover speed, means for varying the flow of energy to said prime mover to correct greater variations in prime mover speed, a hydraulic servo-motor, means enabling said servo-motor to first operate said brake load varying means and then operate said energy varying means, means including a control valve for supplying motive liquid to said servo-motor,`

and means responsive to rotation of the third leg of sai/id differential for operating said control valve'.

7. A speed controller for a prime mover, comprising a three legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg driven at a measured speed whereby the third leg is rotated in response to any variation in the speed Jof said prime mover relative to said measured speed, a pump driven by said prime mover, a valve for resisting the discharge of liquid by said pump to thereby impose a brake load upon said @rime mover, means for varying the flow of energy to said prime mover to thereby vary the speed thereof, a hydraulic servo-motor for operating said valve and said energy varying `means, means including a control valve for supplying motive liquid to said servo-motor, and means responsive to rotation of the third leg of said differential for operating said control valve.

8. A speed controller for a prime mover, comprising a three legged differential having a iirst leg driven by said prime mover at a speed lproportional to the speed thereof and a second leg driven at a measured speed whereby the third leg is rotated in response to any variation in the speed of said prime mover relative to said measured speed, a pump driven by said prime mover,

a valve for resisting the discharge of liquid by said pump to thereby impose a brake load upon said prime mover and correct slight variations in prime mover speed, means for varying the flow of energy to said prime mover to correct greater variations in prime mover speed, a hydraulic servo-motor, means enabling said servoinotor to first operate said valve and then operate said energy varying means, means including a control valve for supplying liquid to said servo-motor to operate the same, and means responsive to rotation of the third leg of said differential for operating said control valve.

9. The combination, with a prime mover, of a chronometric mechanism having an escapement and a shaft fixed to said escapement and rotating intermittently at a constant overall speed during operation of said mechanism, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said shaft whereby the third leg of said differential is caused to rotate in a given direction during each interruption in the rotation of said shaft, a lever carried by said third leg and rotatable-therewith, means resisting rotation of said third leg in said direction and causing said third leg to rotate in the opposite direction during rotation of said shaft whereby` said lever is oscillatedthr'ough a given arc which remains stationary as long as the prime mover speed remains proportional to the overall speed of said shaft but which moves in one dlrection or the other sin response to a variation in prime mover speedgmeans for varying the speed of said prime mover, a valve for controlling said speed varying means, an abutment carried by said valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said valve in said direction, means for moving said val-ve in the opposite dlrection upon said lever swinging in the opposite direction, and a dashpot for retarding the movement of said valve y,/in said opposite direction.

10. The combination, `with a prime mover, of a chronometric mechai'liism having an escapement and a shaft' xed/ to said escapement and rotating intermittently at a constant overall speed during operation of said mechanism, a. three legged differential having one leg continuously driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said shaft whereby the third leg of said differential is caused to rotate in a given direction during each interruption in the rotation of said shaft, a lever carried by said third leg and rotatable therewith, means resisting rotation of said third leg in said direction and causing said third leg to rotate inthe opposite direction during rotation of said shaft whereby said lever is oscillated through a given arc which remains stationary as long as the `prime mover speed remains proportional to the overall speed of said shaft but which moves in one direction or the other in response to a variation in prime mover speed, means for imposing a brake load upon said prime mover, a valve for controlling the application of said brake load to said prime mover and shiftable in one direction or the other to vary said brake load and thereby correct variations in prime mover speed,

an abutment carried by said valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said valve in said direction, means for moving said valve in the opposite direction upon said lever swinging in the opposite direction, and a dashpot for retarding the movement of said Valve in said opposite direction.

11. The combination, with a prime mover, of a chronornetric mechanism having an escapement and a shaft fixed to said escapement and rotating intermittently a a constant overall speed during operation o/f said mechanism, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to,y the 'speed ,thereof and a second leg connected to said shaft whereby the third leg of said ,differential is caused to rotate in a given direction during each interruption in the rotation of said shaft, `a lever carried by said third leg and rotatable therewith, means resisting rotation of said third leg in said direction and causing said third leg to rotate in the opposite direction during rotation of said shaft whereby said lever is oscillated through a given arc which remains stationary as long as the prime mover speed remains proportional to the overall speed of said shaft but which moves in aasaaie said valve being shiftable in vone directionl or` as long as the prime mover speed remainsfpro'- portional to the mean speed of said escape wheel but which moves in one direction or'the other :Qin response to a variation' in prime mover, speed,

the other to vary said brake-load andthereby correct variation in prime mover speed, an abutment carried by said valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said valve in said direction, means for moving said valve in the opposite direction upon said lever swinging in the .opposite direction, and a dashpot for retarding the movement of said valve in said opposite direction. A

12. The combination, with a prime mover, of a chronometric mechanism having an escapement and a shaft fixed to said escapement and rotating intermittently at a constant overall speed during operation of said mechanism, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said shaft whereby the third leg of said differential is caused to rotate in a given direction during each interruption in the rotation of said shaft. a lever carried by said third leg and rotatable therewith, means resisting rotation of said third leg in said direction and causing said third leg to rotate in the opposite direction during rotation of said shaft whereby said lever is oscillated through a given arc which remains stationary as long as the prime mover speed remains proportional to the overc all speed of said shaft but which moves in one direction or the other in response to a variation in prime mover speed, means for imposing a brake load upon said prime mover, means for varying said brake load to thereby correct small variations in prime mover speed, means for varying the iiow of energy to said prime mover to thereby correct greater variations in prime mover speed, a fluid operated servo-motor for operating said load varying means and said energy varying means, means for supplying motive fluid to said servo-motor, a valve for controlling the operation of said servo-motor, an abutment carried by said valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said valve in said direction, means for moving sai-d valve in the opposite direction upon said lever swinging in the opposite direction, and a dashpot for retarding the movement of said valve in said opposite direction.

i3. The combination, with a prime mover, of a chronometric mechanism having an escape wheel which rotates intermittently at a predetermined constant mean speed during operation of said mechanism, said escape wheel being alternately rotated through a given angular distance and then stopped, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to the escape wheel whereby the third leg of said differential is caused to rotate in a given direction ing said third leg to rotate in the opposite direction during each intermittent rotation of said l escape wheel whereby said lever is oscillated through a given arc which remains stationary means for varying the .Speed of said prime mover,

i. a valve -for controlling'sa'id speedvaryingfmeans,

an abutment carrie'd'by'said valve and arranged in the pathv of said lever to enable said `lever as it swings in lone direction to shift said valve in said direction, means for moving said valve in the opposite direction upon` sai-d lever swinging in the opposite direction and means for retarding the movement of said valve in said opposite direction whereby said valve moves through a very short distance regardless vof the movement of said lever through a much greater distance.

14. The combination, with a prime mover, of a chronometric mechanism having an escape wheel which rotates intermittently at a predetermined constant mean speed during operation of said mechanism, said escape wheel being alternately rotated through a given angular distance and then stopped, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to the speed thereof and. a second leg connected to said escape Wheel whereby the third leg of said differential is caused to rotate in a given direction during each interruption in the rotation of said escape wheel, a lever carried by said third leg and rotatable therewith, means resisting rotation of said third leg in said direction and causing said third leg to rotate in the opposite direction during each intermittent rotation of said escape wheel whereby said lever is oscillated through a given arc which remains stationary as long as the prime mover speed remains proportional 'to the mean speed of said escape wheel but which moves in one direction or the other in response to a variation in prime mover speed, means for imposing a brake load upon said .prime mover, a valve for controlling the application of said brake load to said prime mover and shiftable in one direction or the other to vary said brake load and thereby correct variations in prime mover speed, an abutment carried by said valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said valve in said direction, means for moving said valve in the opposite direction upon said lever swinging in the opposite direction. and means for retarding the movement of said valve in said opposite direction whereby said valve is moved through a very short distance regardless of the movement of said lever through a much greater distance.

15. The combination, with a prime mover, oi a chronometric mechanism having an escapement and a shaft fixed to said escapement and rotating intermittently at alconstant overall speed during operation of said mechanism, a three legged differential having one leg continuously driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said shaft whereby the third leg oi' said diierential is caused to rotate in a given direction during each interruption in the rotation of said shaft, a lever carried by said third leg and rotatable therewith, means resisting rotation of said third leg in said direction andcausing said third leg to rotate in the opposite direction during rotation of said shaft whereby said lever is oscillated through a given arc which remains stationary as long as the prime mover speed remains proportional to the overall pose a brake load upon said prime mover, said valve being shiftable in one direction or the other to vary said brake load and thereby 'correct small i variations in prime mover speed, means for varying the iiow of energy to said prime mover to thereby correct greater variations in prime mover speed, a fluid operated servo-motor for operating said throttle valve and said energy varying means, means for supplying'motive fluid to said vservomotor, a control valve for controlling the operation of said servo-motor, anabutment carried by said control valve and arranged in the path of said lever to enable said lever as it swings in one direction to shift said control valve in said direction, means for moving said control valve in the opposite direction upon said lever swinging in the opposite direction, the movement of said control valvein said opposite direction.

16. A speed controller for a prime mover, comprising means for imposing a brake load upon said prime mover, a chronometric mechanism driven by power derived from said prime mover, a legged differential having a first leg driven by said prime mover at a speed proportional to the speed thereof and a second leg connected to said chronometric mechanism and driven at a speed proportional to the speed thereof whereby any variation three in the speed of said prime mover relative to the speed of said chronometric mechanism causes rotation of the third leg of said differential, means for varying the flow of energy to said prime mover to thereby vary the speed thereof, and means responsive to rotation of said third leg for rst varying the brake load on said prime mover and then operating said energy varying means to thereby correct said variation in prime mover and a dashpot for retarding speed.

17. A speed controller fof aprime mover, comprising a pump driven by said prime mover, a chronometric mechanism driven by power derived fromsaidrprim'e mover, a three legged differential of the third leg of said differential,` a valve for resisting the discharge of liquid by said pump to thereby impose a brake load upon said prime mover, means for varying the ow of energy to said prime mover to thereby vary the speed thereof,` and means responsive to rotation of the third leg of said diiferential for ilrst operating said valve to vary the resistance to the flow of liquid therethrough andv thereby vary the brake load upon said prime mover and then operating said energy varying means.

WALTER FERRIS. 

